Per a request in another thread, I will try and set this out briefly, and in one place, and I hope others will elaborate and correct me, and fill in stuff I forgot, so that I don't look too foolish.

"Dha" is a Burmese term that simply means "blade." We in the West use it to refer to a variety of sword-and dagger-length weapons that are used by a variety of people in continental Southeast Asia (which means present-day Burma/Myanmar, Thailand, Laos, Cambodia and Vietnam). The use of what we call a dha also extends into the extreme northeast of India, in the Assam and Naga hills, and into southern China in what is today Yunnan Province.

Swords: A sword dha, called a dha lwe in Burmese and a darb or daab in Thai, is any sword with a single-edged blade that generally widens progressively toward the tip, but not more than to a length/tip width ratio of perhaps about 5/1 or 6/1 (blades with very wide tips are called dha ma - choppers - in Burma). The cut-off is sort of subjective, at least for me. Spines are rounded, flat, peaked or various combinations. Rarely there is a groove in the spine. False edges are not uncommon. Blades are often engraved or decorated with koftgari or inlay, on the flat and spine, some very elaborately. They are often of laminated or inserted-edge construction, and often have a hardened edge. Tangs are usually very short, and "blind," i.e., inserted into the handle and held by pressure or adhesive. I have never seen a pinned tang.

The tip can be upswept, angled (forward or reverse), square, round, convex, spear-shaped or "sheep's foot" (where the spine curves down toward the edge). There are specific names for each of these tips in Thai (see the Glossary page at The Dha Research Index).

Handles are almost always of a round cross section, and can vary in length from about hand-width to about equal in length with the blade. A pommel may or may not be present, and is either spherical, a sort of flattened cone, top-shaped or lotus-shaped (there is a variation of this that looks sort of like a conch shell). Sometimes it is just a simple cap on the handle. I have never seen a disk-shaped pommel, though some round ones approach a lense shape (wide axis perpendicular to the handle). There is generally no guard, though the ferrule often flares toward the blade; some Thai darb have a small tsuba-style guard, and some "montagnard" dha have a diamond-shaped guard that is almost more of a spacer as it barely exceeds the diameter of the handle. "Village" dha often have neither pommel nor ferrule.

Scabbards are generally wood, often with metal bands, or partial or complete metal sheathing. "Village" dha tend to have braided cord or rattan bands. Scabbards usually start with a round cross-section equal in diameter with the ferrule, and progressively transition to a flat cross-section, either square-ended, rounded or more rarely up-swept. In Burmese dha, the scabbard is usually suspended from a cord baldric hung from one shoulder; in Thailand the scabbard can be hung from the shoulder, across the back, or as a crossed pair on the back (this might be the case in other parts of SEA, but I just don't know).

Daggers: Daggers are called dha hmyaung in Burma (not to be confused with a simple utility knife, which is called a dha mauk). I don't know what they are called in Thailand and other parts of SEA. They basically resemble miniature dha lwe, with a single edge and either upswept of spear-shaped tip. Like the swords they can have laminated or inserted edge construction, and hardened edges. Handles are sized to fit the hand, and in style follow those found in swords. Scabbards again are smaller versions of those of sword-length dha, though there is a style of dagger scabbard that has a round cross-section. There is another type of knife used in SEA that has a down-ward curved blade, similar to a yatagan or piha ketta, which we Westerners call a "priest knife" because, surprise, it is used by priests.

Here are a few examples of swords:
A couple daggers:
And a priest knife:

More can be found by searching "dha" on this and the old forum, and at the link above.